Refractories



Patented Apr. 20, 1937 g UNITED STATES PATENT OFFICE Frederic A. Harvey and Raymond E. Birch, Pittsburgh, Pa., assignors to Harbison-Walker Refractories Company, Pittsburgh, Pa., a corpora tion of Pennsylvania No Drawing. Application June 4, 1935,- Serial No. 24,988-

Claims. (Cl, IM -9) This invention relates to refractories, more cent. The most highly serpentinized and most particularly to chrome ore refractories. highly steatitized. olivines are, in general, not It is among the objects of the invention to prosuitable for the purposes of the present invention, videchrome ore refractories possessing improved nor other olivine minerals containing more than 5 characteristics, particularly with regard to minor amounts of alteration products. How- 5 strength and weight, as compared with those ever, we have successfully used olivines which manufactured heretofore, which exhibit relativecontained as much as 10 to per cent of talcly low shrinkage upon burning and reheating, in plus-serpentine, and depending upon the standwhich desirable characteristics of chrome ore reards of refractoriness which the product must 0 fractories, such as resistance to acid and basic meet, it may be possible for some purposes to 10 conditions, and relatively low porosity, are reuse olivine-rich materials containing somewhat tained wholly or in such large part as not to regreater percentages of these and other hydrous duce their desirability, and which are relatively alteration products.

cheap and readily made. As exemplifying the benefits to be derived from 15 Chrome refractories are desirable for many the practice of the invention, reference may be uses because they are substantially neutral in made to refractories made from (a) a chrome action when exposed to either acid or basic slags, ore containing about.32.7 per cent of CrzOs, 14.5 and because chrome ore is relatively cheap and per cent of FeO, 17.8 per cent of MgO, 29.5 per is one of the more refractory of the materials cent of A1203, and the balance consisting of other commonly applied to such uses. Certain disadsubstances in small amounts, and (b) an olivine 20 vantages, however, have militated against chrome containing about 41 per cent of S102, 49 per cent refractories used prior to our invention. For of MgO, 7.7 per cent of iron calculated as FeO, instance, they have been characterized by rela- 0.8 per cent of A1203, 0.4 per cent of Ca0, 0.3 tively low softening temperatures; consequently, per cent of chromium calculated as Cr203, and

their use has been limited to temperatures suban ignition loss of 0.8 per cent. A mixture of 75 25 stantially below the melting point of chrome ore, per cent of that chrome ore and 25 per cent of and it has been necessary to restrict the loads olivine was ground to about 4 mesh and the applied to the refractories. Moreover, they have ground mixture, after tempering with water, was exhibited other properties undesirable in refracformed into bricks and burned to about 2600 3O tories for use at high temperatures, such as ap- F. Brick for comparison were made in the same preciable volume shrinkage upon reheating. manner from 100 per cent of the same chrome This invention is predicated on our discovery ore. Upon test the-bricks showed the following that its stated objects may be attained by makproperties:

ing chrome refractories from mixtures of at least 50 per cent of chrome ore with natural v 75% chrome 35 olivine in an amount not exceeding the chrome F2575 cmttfl'tm ore. Thus the refractories provided by the in- 01mm vention comprise from about 5 to not exceeding T t H 1 fb k d empera ure 0 B1 1H9 0 [10 11B er about 50 per cent of olivine and the balance sub load arm/Sq 27000 24000 .111 40 stantially all chrome ore, and most advantage- Volume change when reheated for 5 40 hours at 2912 F 0. 1% --2. 5%

ously they are composed of chrome ore with from about 20 to about 40 per cent of olivine. I

The olivines used in the practice of the inven- It p therefore, that brick made in acti are of th Mg-Fe type, Preferably t 1- cordance with this invention possess a substanivine rock is high in its magnesium orthosilicate a y higher temperature of failure, a d at 45 content, examples of suitable rocks being the the Volume Change p reheating has become dunites and peridotites. The iron content of the practically as a d With a high Shrinkolivine should be relatively low, and most adage p n r h i f in y hr m ore brick. vantageously should not exceed about 10 per The foregoing results are characteristic of the 5 nt calculated as FeO In the practice of the properties achieved through the practice of this invention satisfactory results have been obtained invention, indicating t al nc ease in with a dunite containing about 40.6 per cent of strength with great reduction, 01 virtual elimi- SiOz, 47.6 per cent of MgO, 7.5 per cent of FeO, nation, in Shrinkage p reheating. Although 1.1 per cent of A1203, 0.8 per cent of CI203, 0.1 benefits are obtained by making refractories from per cent of Ca0, and an ignition loss of 1.2 per chrome ore and more than about 5 per cent of 55 olivine, with the olivine not exceeding the amount of chrome ore, particularly desirable results are attained using mixtures of chrome ore and about to 40 per cent of olivine because within this range of compositions especially suitable combinations of properties are obtained. For instance, using 20 to 40 per cent of olivine the temperature of failure under load is increased materially as compared with brick made from chrome ore alone in accordance with prior practice, and within this range the strongest mixes, as indicated by the moduli of rupture, are produced. Within this range also there is minimum change in linear dimensions in burning, so that the burning shrinkage is very slight, as may be desirable in refractories. Moreover, these compositions show minimum change in linear dimensions upon reheating, this change taking the form of shrinkage and being generally of the order of about 0.5 per cent, and not exceeding about 2.0 per cent. Moreover, the porosity is relatively low for refractories of this type.

We have found also that the brick possess desirable weight characteristics. For instance,

' those containing from about 20 to about 40 per cent of olivine exhibit weights from about 170 to 180 lbs. per cubic foot as compared with brick made from chrome ore alone, which may Weigh as much as about 196 lbs. per cubic foot. This is of importance because refractory brick of this type are commonly sold on a weight basis, and a reduction in weight thus means that the buyer obtains more brick per ton than with heavier brick, or, stated another way, the shipping cost per brick is less because there are more brick per ton.

In the practice of the invention the chrome ore and olivine, suitably grain sized, are intimately mixed in accordance with desired practice. Ihe two materials may be ground together, or they may be ground separately. The particular grain size and relation of grain sizes of the two materials does not seem to be critical in achieving the benefits of the invention, but they may be varied to vary properties, such as bulk density and porosity, of the resultant fired refractory in accordance with relations understood by those skilled in the art.

If the refractory is to be used as a lining or ramming mix, or for similar purposes, it is necessary only to produce an intimate mixture of the two materials in appropriate proportions and suitably grain sized. Where shaped refractories are to be formed the materials are mixed in a suitable mixer and tempered with water or other suitable liquid according to customary practice, for which reason mixing in an ordinary wet pan may be carried out. The prepared mixture is then shaped, advantageously under high pressure, and the bricks then dried and burned.

If the bricks are to be shipped unburned it will usually be desirable to add a temporary binder' such as the organic binders and others which are well known and available in the art.

For some purposes it may be desirable also to add a mineralizer such as borax, fluorspar, cryolite, and others of which a variety are used in the production of refractories. Usually the mineralizer will be present in rather small amount, usually not to exceed about 5 per cent.

In the practice of the invention a part or all of the chrome ore, alone or with olivine, may be calcined, if desired, prior to forming the batch, or if desired for any reason it may be fused and crushed to prepare it for the manufacture of the refractories. Likewise, the chrome ore and the olivine, or either, may be subjected to the various purification and beneficiation treatments, such as magnetic separation, applied to removal of impurities or to improve the quality of the mineral.

While the invention has been described chiefly with reference to the production of shaped and fired articles, nevertheless it contemplates also the use of refractory compositions as ramming mixes, for forming linings, or the like, which are burned in place. Similarly, the brickmay be formed and dried, shipped in that condition, and laid up into the desired structure, being burned in service.

According to the provisions of the patent statutes, we have explained the principle and. mode of applying our invention and have described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

We claim:

1. A refractory material comprising about 5 to 50 per cent of olivine of high magnesium orthosilicate content, and the remainder substantially all chrome ore.

2. A burned refractory material comprising from about 5 to 50 per cent of olivine of high magnesium orthosilicate content, and the remainder substantially all chrome ore.

3. A refractory material comprising from about 20 to 40 per cent of olivine of high magnesium orthosilicate content, and the remainder substantially all chrome ore.

4. A refractory material comprising about 75 per cent of chrome ore, and per cent of olivine of high magnesium orthosilicate content.

5. A burned refractory material comprising about 75 per cent of chrome ore, and 25 per cent of olivine of high magnesium orthosilicate content.

FREDERIC A. HARVEY. RAYMOND E. BIRCH. 

